The present invention generally relates to a medical device for positioning a stent delivery or dilatation balloon catheter within the vascular system of a patient. More specifically, the present invention discloses a hub assembly unit providing an operator the ability to finely adjust the positioning of a stent delivery or a balloon dilation catheter within a patient""s vascular system.
Percutaneous Transluminal Coronary Angioplasty (PTCA) is a well-established procedure for dilating stenosed vessel regions within a patient""s vasculature. In this procedure, a balloon angioplasty catheter is introduced into the vasculature, typically through an incision in the femoral artery in the groin. The balloon catheter is then advanced through the femoral artery, through the aortic arch, and into the artery to be treated. The balloon portion of the dilation catheter is specifically advanced across the stenosis or constricted vessel, wherein the balloon is inflated. Inflation of the balloon dilates the surrounding vessel and/or displaces the plaque the forms the stenosis. The resulting treated vessel is then characterized by a greater cross-sectional area permitting additional blood flow through the previously occluded or constricted region.
Over a period, a previously dilated vessel may narrow. Often this narrowing is a result of a vessel xe2x80x9creboundingxe2x80x9d from an angioplasty procedure. In order to prevent vessel rebounding, stents are often deployed concurrently with a vessel dilation procedure. A stent is positioned across the treated dilated region of vasculature where it is radially expanded utilizing a stent delivery catheter. Once properly seated within the vessel wall, the frame of the stent opposes any inward radial forces associated with vessel rebounding.
During a PTCA procedure, it is often necessary to finely adjust the positioning of the stent delivery or balloon dilatation catheter. Improper placement of a stent within a desired region can cause a portion of the treated vessel to narrow, substantially decreasing the benefits of the initial medical procedure.
Currently, a physician positions the distal end of a balloon dilatation or stent delivery catheter by manually pushing or pulling on the proximal end of the catheter. These pushing and pulling motions must be transmitted through the entire length of the catheter shaft to affect the catheter""s distal tip. The catheter shaft in a medical procedure, however, is usually quite intricately routed within a patient""s vascular system. The vascular pathlength from the femoral artery to the desired treatable artery is usually long and quite tortuous. Manipulations made by the physician at the catheter""s proximal end, therefore, do not necessarily directly translate to the same movements at the catheter""s distal end.
Catheters have a natural tendency to compress or elongate irregularly when manipulated proximally. More specifically, when advancing a catheter from the catheter""s proximal end, the catheter tends to advance into and through the curves of vessel walls where they contact a greater surface area. An advancing catheter, therefore, requires greater force and displacement at the catheter""s proximal end to move the catheter a desired length at the catheter""s distal end. In contrast, a retracting catheter straightens through the curvature of vessel walls causing the catheter to elongate when withdrawn.
A physician is often required to make a series of advancements and retractions of the catheter to effectively navigate through the tortuous vascular system of a patient. Each advancement and retraction compresses or elongates various sections of the catheter. These compressions and elongations store potential energy throughout the length of the catheter shaft. Coarse manipulations by a physician at the catheter""s proximal end may affect the arrangement of these compressions and elongations. Specifically, pulling and pushing of the proximal end of a catheter may cause an unaccounted for release of stored potential energy in the catheter shaft. This unaccounted for release of energy is called the xe2x80x9cbacklashxe2x80x9d phenomenon. Backlash causes a physician to experience either a sudden burst or a lag in relative movement of the distal end of the catheter. This unaccounted for release functionally decreases accuracy in positioning a catheter within a patient""s vascular system. Further, even without the issues related to stored energy and backlash, making the necessary fine adjustments requires more time and is less accurate than desirable.
Further complications arise when a physician attempts to inflate the stent delivery or balloon dilation catheter. Before inflation, a physician must tighten the hemostasis valve around the catheter. Tightening the hemostasis valve, however, may cause the stent delivery catheter to move out of position. Consequently, the physician is forced to reposition the catheter once again across the desired vascular region. As a result, the time spent repositioning the distal end of a catheter causes unnecessary medical expense and further trauma to the patient.
The present invention provides a medical device permitting fine adjustments of the distal end of a stent deployment or balloon dilatation catheter. In particular, the present invention discloses a hub assembly unit providing a fine adjustment mechanism. The fine adjustment mechanism extends or contracts the length of the hub assembly unit in controlled incremental units. These controlled fine displacements are then translated directly to the stent delivery or balloon dilation catheter.
Contrary to coarse adjustments, fine displacements have been found to conserve stored potential energy within a catheter system. A physician may therefore incrementally adjust the displacement of the hub assembly unit of the present invention to accurately and predictably advance or withdraw a stent delivery or balloon dilation catheter. In the present invention, fine adjustments made at the proximal end of the hub assembly unit directly translate to similar adjustments at the distal end of the catheter. Thus, the hub assembly unit of the present invention allows a physician to precisely position a stent delivery or balloon dilation catheter at a desired point within a desired region of a patient""s vasculature.